Cellulosic textile materials are dyed by printing, exhaust and padding processes. Fiber-reactive dyes, which are capable of entering a covalent bond with the fiber during the dyeing process, are particularly important dyes for cellulosics, since the dyeings obtainable therewith are notable for good wetfastnesses in particular, which is very difficult or impossible to achieve with non-fiber-reactive dyes. However, the covalent bond between the fiber-reactive dyes and the fiber generally only comes about when the dyeing process is carried out under alkaline conditions. The alkalis used are alkali metal carbonates, alkali metal bicarbonates and alkali metal hydroxides or mixtures thereof plus, in pad dyeing, alkali metal silicates, optionally together with an alkali metal hydroxide or carbonate, the term alkali metal including lithium as well as sodium and potassium. It is mixtures of alkali metal carbonates and alkali metal hydroxides in particular which are highly efficacious and are preferred, although the alkali system used in a particular case is chosen according to the specific fiber-reactive grouping of the dye and the specific dyeing process.
An ultrashort liquor dyeing process, for example the padding process, whereby the treatment liquor is applied to a textile material and the excess liquor on the textile material is then squeezed off, can be carried out according to both a one-stage and a two-stage procedure. The two-stage process procedures, whereby the textile material is initially impregnated with a dye solution to a certain wet pickup, then dried and subsequently overpadded in a further impregnating step with an alkaline electrolyte salt liquor, has the disadvantage of high machine usage and of utilizing electrolyte salts in the second process stage. In contrast, in a one-stage process, the complete treatment liquor, which contains both the fiber-reactive dye and the alkali with or without further auxiliaries, is applied to the textile material in one operation which is followed by the step of fixing the dye on the textile material.
One of these one-stage process procedures is the pad-cold batch process, which is chiefly used for dyes which contain a fiber-reactive group. In this case, the alkalinically binding agents used are frequently alkali metal silicates in the form of waterglass (Na2O: SiO2 in a ratio of 1:2 to 1:3.5), between 60 and 130 g of waterglass of 38xc2x0 Bxc3xa9 and 6 to 40 ml of approximately 32% strength by weight aqueous sodium hydroxide solution being added per liter of the dyeing liquor, depending on the target depth of shade. Waterglass has the advantage that it has a pH buffering effect and increases the stability of padding liquors of reactive dyes. Another positive effect of using waterglass in the padding process is that the edges of the material to be dyed will have the same depth of shade and hue, since waterglass forms a protective film against the carbon dioxide in the ambient air. Yet, the use of waterglass is not wholly beneficial. Examples of disadvantages are that waterglass tends to crystallize and thus tends to soil the equipment; that it is not possible to neutralize the textile material prior to the washing step; and that the use of steam for fixing the dyes is not always possible; moreover, unattractive hand effects may arise.
The literature describes attempts to remedy such disadvantages. For instance, in U.S. Pat. No. 4,555,348, an aqueous buffer system which has a pH between 11 and 13 and which contains various phosphate salts is added to dyeing liquors. Such an aqueous buffer system is undoubtedly suitable in dyebaths for exhaust processes, but not for dyeing by padding processes. Furthermore, the buffer system has the disadvantage that phosphate salts create environmental problems in water treatment plants.
The art of dyeing by the pad-cold batch process generally features the addition to the dyeing (padding) liquor of a specific amount of sodium hydroxide solution, decided on the basis of the amount of dye present in the padding liquor, and also of about 30 g/l of electrolyte salt, such as sodium chloride or sodium sulfate. However, padding liquor stability is generally unsatisfactory and leads to yield losses in the color strength of the dyeings.
However, the prior art also teaches that sodium carbonate alone or sodium hydroxide/sodium carbonate mixtures can be used in the case of highly fiber-reactive systems, for example dichloroquinoxaline, difluoromonochloropyrimidine and monofluorotriazine dyes. In the case of the pure sodium carbonate method, the lower pH will sometimes lead to uneconomically long fixing times, whereas the sodium hydroxide/sodium carbonate variant will sometimes bring about an increased reactive dye hydrolysis. These systems are less suitable for vinyl sulfone dyes, since the fixing time lengthens significantly and compromises the economics of the dyeing process. In addition, the art as it presents itself at present teaches in relation to the sodium hydroxide/sodium carbonate method that the amount of sodium hydroxide used varies with the dye concentration, while the sodium carbonate is always added as a fixed proportion.
It is an object of the present invention to provide, in the field of dyeing by ultrashort liquor processes, for example by padding processes, especially by the pad-cold batch process, an aqueous alkaline formulation which can be added to the dyeing liquor without creating the disadvantages mentioned.
It has now been found that, especially as replacement for waterglass in ultrashort liquor processes, such as padding processes, an aqueous solution comprising sodium hydroxide and potassium carbonate in a molar ratio of 1:1.7 to 1:0.5, preferably 1:1.5 to 1:1.1, particularly preferably 1:1.2 to 1:0.7, surprisingly has the desired advantageous effect. Moreover, the alkaline formulation of the invention has the particular advantage in use of being meterable. And the use of urea in the dyeing process can be dispensed with. Examples of formulations according to the invention which are suitable for production are aqueous solutions of 39.6 kg of sodium hydroxide and 110 to 163 kg of potassium carbonate in 250 to 1000 liters of solution.
The invention thus provides this solution and also a method of using it in aqueous ultrashort liquors, such as padding liquors, which contain fiber-reactive dyes. They may include customary dyeing auxiliaries, such as an anionic wetting agent.
The solution according to the present invention may also contain potassium hydroxide. It is preferred to replace an amount of from 10 to 40 mole % of sodium hydroxide by potassium hydroxide.
The solution according to the present invention may additionally contain further ingredients like for example sodium chloride, sodium silicate, sodium metasilicate, water glass, Glauber""s salt, phosphates like tri-potassium phosphate or tri-sodium phosphate, alkali metal citrates, alkali metal polyacrylates or ethylenediaminetetra-acetic acid (EDTA) and its salts in amounts of less than 5% by weight, preferably less than 2% by weight based on the total weight of the solution. It is, however, particularly preferred if the solution according to the present invention is free of any such further ingredients.
The alkaline formulation of the invention is used according to the invention by mixing an aqueous solution of one or more fiber-reactive dyes, which optionally includes customary dyeing auxiliaries, with the alkaline formulation of the invention (generally 100 liters of an aqueous dye solution comprising about 10 to 12,000 g of dye being admixed with 2 to 17 liters of the alkaline formulation of the invention) and using the resulting alkaline dyeing liquor to impregnate a cellulosic textile material in a conventional manner, for example by spraying or padding, and fixing the dye or dyes under process conditions customary for fiber-reactive dyes.
The invention thus also provides a process for dyeing cellulosic textile material by mixing an aqueous dye solution which per liter contains for example about 0.1 to 120 g of one or more fiber-reactive dyes and optionally customary dyeing auxiliaries, with the alkaline formulation of the invention, for example with 20 to 170 ml, based on 1 liter of the dyeing solution, applying the resulting alkaline dyeing liquor to the cellulosic textile material in an amount of 60 to 100% by weight, based on the weight of the material, for example by spraying or padding, preferably by means of a customary padding process, and fixing the dye or dyes under process conditions customary for fiber-reactive dyes.
Since the alkaline formulation of the invention is easily meterable into the dye solution, even in small amounts and steps, to form the padding liquor, the dyeing procedure is also easily carried out continuously; the alkaline padding liquor can thus be formed continuously, which ensures its stability even in the case of critical dyes.
Dyeing procedures which are usable according to the invention include the usual impregnating (padding) dyeing processes for applying fiber-reactive dyes to and fixing them on cellulosic textile materials, for example the pad-cold batch processes, the pad-dry-pad-steam, pad/air-steam, pad-dry-thermofix, pad-steam and thermosol/pad-steam processes. The dyeings obtainable therein are notable for better washoff, neutralizability (nonexistent in the case of waterglass because treatment in an acidic bath is not possible without SiO2 formation) and better hand.
A preferred ultrashort liquor dyeing procedure is the pad-cold batch process, whereby the alkaline dyeing liquor (dye solution) is pad-mangled onto the fabric and the padded fabric is then rolled onto a batching beam and left at room temperature on the beam for 4 to 24 hours. The fixing phase is followed by a customary washoff process, in which the material may also be acidified.
Dyeing by ultrashort liquor techniques may be performed for example according to the correlations shown in FIG. 1, between the concentration of dye and the amount of alkaline formulation in the padding liquor necessary for effecting fixation. Alkaline formulation A, for example, which is an aqueous solution of 39.6 g of sodium hydroxide and 163 g of potassium carbonate per 1000 ml and of which 49 ml is used for the lowest customary dye concentration, requires that an additional 0.1 to 0.11 ml be used of it per 0.1 part by weight of dye.
Similarly in the case of alkaline formulation B, which is an aqueous solution of 146 g of sodium hydroxide and 390 g of potassium carbonate per 1000 ml, the alkaline dyeing liquor requires an additional 0.04 to 0.045 ml of alkaline solution B per 0.1 part by weight of dye as well as the 20 ml of this alkaline formulation B required for the lowest customary dye concentration.
The alkaline dyeing liquor obtainable by mixing the alkaline formulation of the invention with an aqueous solution of fiber-reactive dyes has high padding liquor stability and can be used in all ultrashort liquor processes, such as padding processes, hitherto customarily utilizing alkali metal silicates (waterglass) as alkali donors and/or pH buffering agents, and replace the latter therein.
By cellulosic textile materials are meant all fiber materials which comprise or consist of cellulosic fibers, for example cotton, jute or linen, and which have been processed into textile structures, especially wovens and knits, and also such materials composed of cellulosic natural fiber materials which have been modified, for example regenerated cellulose, such as filament viscose, and amino-modified cellulose fibers as known for example from U.S. Pat. Nos. 5,507,840; 5,565,007; and 5,529,585; from European Patent Application Publication No. 0 615 311; and from Serman Offenlegungsschrift 19 519 023.
Fiber-reactive dyes are universally and extensively known and described in the literature. As fiber-reactive dyes particular emphasis must be given to those which possess a fiber-reactive radical of the vinyl sulfone series, for example vinylsulfonyl or an ethylsulfonyl which is xcex2-substituted by an alkali-eliminable substituent, such as xcex2-sulfatoethylsulfonyl, xcex2-acetoxyethylsulfonyl, xcex2-chloroethylsulfonyl or xcex2-thiosulfatoethylsulfonyl, also fiber-reactive radicals of the chlorotriazinyl, fluorotriazinyl, dichloroquinoxalinyl, fluoropyrimidinyl and chlorofluoropyrimidinyl series, and also dyes possessing combinations of such fiber-reactive groups.